1. Field of the Invention
The present invention relates to the field of semiconductor manufacturing, and particularly relates to a polishing apparatus and exception handling method thereof.
2. Description of Prior Art
With the continuous development of the semiconductor manufacturing process, processes have entered nanometer era. The manufacturing of VLSI requires tens of millions of transistors and interconnects to be formed within an area of several square centimeters; and the multilayer metal technology makes the integration of millions of transistors and interconnects within a single integrated circuit possible. The chemical mechanical polishing (CMP) process is a major process of planarization in the multilayer metal technology.
CMP process is introduced to the IC manufacturing industry in 1984 by IBM, and is firstly used to planarize inter metal dielectric (IMD) in back channel process. The CMP process is then used to planarize tungsten, and then shallow trench isolation (STI) and copper. CMP has become one of the most important and fastest developed technologies in IC manufacturing industry.
For the mechanism of CMP, it is described that: a surface layer which is relatively easy to remove is formed by reaction of the surface material of a wafer and polishing liquid, and the surface layer is then mechanically scraped off by polishing pressure and by relative motion between polishing pad and the wafer. Specifically, during the CMP of metal material, polishing liquid is in contact with the surface of the metal material, and metal oxide is generated which is then mechanically scraped off to achieve the effect of polishing. However, when surface of the metal material (especially for copper and aluminum) is exposed to the deionized water or grinding liquid for a long time, the metal material tend to be corroded which causes device failure.
Currently, CMP process is fully controlled by computer. During a CMP process, if there is an abnormal situation, such as pressure or rotation speed exception, the polishing equipment will automatically stop working and send alarm, then waits for device engineers. During the waiting for device engineers, the wafer that is unfinished in the CMP process (including wafers in a grinding stage or in a cleaning stage after grinding) is left in the grinding liquid or cleaning liquid (normally deionized water), which will cause the surface of the metal material be corroded thus affecting the quality of wafers.
A CMP technology is disclosed in US Patent Publication No. US20050112894A1, which includes CMP slurry for forming aluminum film, CMP method using the slurry and method for forming aluminum wiring using the CMP method.